Delineation of the GPR15 receptor-mediated Gα protein signalling profile in recombinant mammalian cells.

The GPR15 receptor is a G protein-coupled receptor (GPCR), which is activated by an endogenous peptide GPR15L(25-81) and a C-terminal peptide fragment GPR15L(71-81). GPR15 signals through the G i/o pathway to decrease intracellular cyclic adenosine 3',5'-monophosphate (cAMP). However, the activation profiles of the GPR15 receptor within G i/o subtypes have not been examined. Moreover, whether the receptor can also couple to G s , G q/11 and G 12/13 is unclear. Here, GPR15L(25-81) and GPR15L(71-81) are used as pharmacological tool compounds to delineate the GPR15 receptor-mediated Gα protein signalling using a G protein activation assay and second messenger assay conducted on living cells. The results show that the GPR15 receptor preferentially couples to G i/o rather than other pathways in both assays. Within the G i/o family, the GPR15 receptor activates all the subtypes (G i1 , G i2 , G i3 , G oA , G oB and G z ). The E max and activation rates of G i1, G i2 , G i3, G oA and G oB are similar, whilst the E max of G z is smaller and the activation rate is significantly slower. The potencies of both peptides toward each G i/o subtype have been determined. Furthermore, the GPR15 receptor signals through G i/o to inhibit cAMP accumulation, which could be blocked by the application of the G i/o inhibitor pertussis toxin.